The invention relates to a device for controlling the brake lights on a vehicle with a brake system, designed to be operated by outside forces.
A device for controlling the brake lights in a motor vehicle is known from German Patent Document DE 199 20 096 A1, where, during an automatic braking operation actuated by outside forces, the brake lamps are controlled automatically. This device has proven to be effective in many situations.
The present invention further improves the brake light control device of this type and in particular provides a brake light control that will guarantee a reliable indication of a braking operation even in a lower speed range of the vehicle, especially in a speed range in the vicinity of a vehicle standing still. In particular, the invention prevents brake light flickering.
The details of the invention will be explained in view of the features disclosed in the specification, drawings, and claims below. An important condition for a brake light control device, according to an exemplary embodiment of the invention, is the presence of an automatic braking operation which is not initiated manually by the driver. Another condition includes the undershooting or reaching a predefined speed threshold limit, and the overshooting of a predefined pressure threshold in at least one hydraulic circuit of the activated vehicle brake, for which the brake light is activated.
For this reason, the inventive device for controlling the brake lights includes a control device for controlling the brakes of the vehicle and at least one brake lamp, which can be actuated by using the control device or by using a separate control unit (hereinafter referred to uniformly as the control device). Therefore, the control device is designed in such a manner that an automatic braking operation (i.e. a braking operation actuated by outside forces) can be carried out as a function of the vehicle's operating conditions. The control device is designed, according to an exemplary embodiment of the invention, in such a manner that during an automatic braking operation, the brake lamp is switched on below a predefined boundary speed, as a function of a braking pressure determined in the activated brake of the vehicle, or as a function of a parameter, correlating to the braking pressure. Below the predefined boundary speed (speed threshold limit), the brake light (the at least one brake lamp) is switched on as a function of the braking pressure of the activated brake of the vehicle or a parameter, correlating thereto (measured or calculated and/or estimated parameters, like the brake torque, braking force at the wheel or the like). Preferably the brake light is actuated below the speed threshold exclusively as a function of the braking pressure or the applied parameter that correlates to the braking pressure. It is advantageous for the predefined speed threshold limit to be above the vehicle speed of zero.
Above the speed threshold limit, the brake light (switched on/off) is actuated in a different way, preferably as a function of the vehicle deceleration, determined, for example, by using acceleration sensors.
The predefined speed threshold limit is applicable to a preferred exemplary embodiment of the invention. In particular, the speed threshold limit can be varied automatically as a function of the vehicle speed (e.g., the current actual vehicle speed at the start time of the braking operation or a speed, determined by a time frame, up to the start time of the braking operation) and/or as a function of the tilt of the vehicle about its transverse axis (e.g., owing to the slope of the road).
In order to switch on or off the brake light in the speed range below the specified speed threshold limit, a switch-on braking pressure threshold value and/or a switch-off braking pressure threshold value (which is preferably different from the switch-on braking pressure threshold value) may be specified. It is advantageous for the exemplary switch-off braking pressure threshold value to be smaller than the switch-on braking pressure threshold value by a predefined pressure differential, so that a sufficiently large switching hysteresis is guaranteed. A brake light that is switched on once in the lower speed range (a speed range below the predefined speed threshold limit) stays on for a logical period of time, and brake light flickering is avoided with certainty. In a possible further exemplary embodiment of the invention, one braking pressure threshold value or both braking pressure threshold values can be designed in an applicable way. It may be advantageous to also vary the braking pressure threshold value as a function of the vehicle speed and/or the tilt angle of the vehicle and/or the weight of the vehicle. In order to bridge, if necessary, any pressure decays, a minimum follow-up time can also be implemented in an applicable way when the braking pressure threshold is not reached.
In order to generate a brake light signal that appears plausible to the following traffic, the exemplary brake light is preferably not switched on until the switch-on conditions have been present without interruption for a specified period of time. If within this period of time the absence of at least one switch-on condition is determined, even for just a short period of time, the time for the monitoring operation (without switching on the brake light) starts to run anew, causing a reset of a timer component.
If the vehicle is brought to a standstill by using an automatic braking operation, a different control of the brake light (in particular, the so-called high mount third brake lamp, arranged usually in the rear window area) is envisioned. A first exemplary design provides that at least one brake lamp that is switched on is held permanently in the on-state until a new restart operation is detected or until the vehicle is deactivated (stopped) by switching off the ignition, or until the function which controls the automatic braking function is deactivated by switching it off manually (for example by actuation of a switching element for activating or deactivating the function by the vehicle occupant).
A second exemplary design provides that after the standstill at least one brake lamp is held in the on-state for a specified period of time. and the at least one brake lamp is not switched off again until after this period of time has expired or when a restart operation is detected or when the stopping of the vehicle is detected or when the function is switched off manually, as described above.
In addition, other criteria may be considered. For example, a vehicle rear space monitoring device can be provided, and the control device may be designed in such a manner that the at least one brake lamp is switched off when the monitoring device has detected another vehicle that is entering the rear space of one's own vehicle and/or approaching said own vehicle. It is advantageous, if upon detection of another vehicle in the rear space of one's own vehicle, said at least one brake lamp is held in the on-state for an additional specified period of time and, following passage of this period of time, is switched off.
Furthermore, the vehicle rear space monitoring device in conjunction with the control device can also be designed in such a manner that upon the approach of another vehicle, which is approaching at a speed above a predefined boundary speed relative to one's own vehicle, the brake light is switched to a second brake light stage. In this second brake light stage, for example, the brightness of the activated brake lamps can be increased, and/or the illuminated area of the brake lamps can be enlarged, and/or additional brake lamps can be activated, and/or the flashing warning lamps can be activated.
Furthermore, the at least one brake lamp can stay in the on-state permanently or for a specified period of time even as a function of the presence of the grade or incline of the road (for example the brake lamp is switched off no later than at the next restart operation or upon deactivation of the vehicle).
Owing to the proposed switch-off and change-over scenarios, an unnecessary blinding of other road users can be avoided in a number of different situations, and an early warning signal can be sent.
In another further development of the control device with respect to switching off the brake light, the control device can be coupled with a navigation system; and said at least one brake lamp can be switched off as a function of the type of environment, determined by the navigation system. In this system, for example, one can distinguish between areas in-town and areas out-of-town, and different switch-off modes can be chosen for the various environments. As an alternative or in addition, a switch-off mode may be assigned as a function of the type of road that is determined (urban street, rural road, freeway) or the current speed limits. Therefore, the maximum allowable speed can be determined with the navigation system or any other detection system (for example, camera systems, traffic guidance systems, or the like) in order to determine the maximum allowable speed.
Furthermore, in the event of automatic braking operations at a very high system deceleration level, for example, automatic braking operations on freeways, the flashing warning system can also be switched on as soon as a correspondingly high deceleration level is reached. As an alternative, however, it is also envisioned not to activate the switch-on procedure of the flashing warning system until after the correspondingly high deceleration level has occurred, thus during a standstill phase of the vehicle.
The braking pressure, as a function of which the brake light is actuated, is determined in an advantageous exemplary manner by using pressure sensors of the brake hydraulic system or by using a model for calculating the braking pressure.
If, in the event of an automatic braking operation, the predefined boundary speed at which the brake light is supposed to be actuated as a function of the pressure (instead, for example, as a function of the deceleration), is not reached, the brake light is already actuated (and/or switched on) so that only the switch-off conditions are controlled as a function of the pressure. In cases where, for example, in a stop and go mode with automatic starting and braking operations, braking operations are initiated below the predefined boundary speed, the brake lamps are switched both on and off as a function of the pressure.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.